The bacterium Asticcacaulis biprosthecum undergoes a dimorphic life cycle during which each cell differentiates two appendages (prosthecae). Surface layers of prosthecae are extensions of surface layers of the cell proper. Certain enzymes have been shown to be localized in prosthecae, and membranes of prosthecae have been shown to be specialized with respect to plasma membranes from which they are derived. Purified prostheceae will be tested for their ability to serve as organelles specialized for the uptake of nutrients from the environment. Various types of mutants of A. biprosthecum will be isolated for use in studies of the dimorphic life cycle. The bacterium Cytophaga columnaris produces an internal membrane system derived from plasma membranes. There is evidence from work with purified membranes to suggest that the internal membranes are sites of synthesis of degradative enzymes. A mutant with altered mesosomal membranes has been isolated and will be characterized to determine the effects of mesosomal alterations on the physiology of the organism. C. columnaris will also be used to study the mechanism of gliding motility. We have isolated a large number of mutants of this organism which are either immotile or exhibit a defective motility. The chemistry and ultrastructure of certain components of the surface layers of mutants and chemistry and ultrastructure of certain components of the surface layers of mutants and wild-type cells will be compared.